Clock skew apart this small biossystemtimeoffset [1][2] is always bad for privacy [3].

When you suspend/save the state of a VM, clock will stop and continue after resume, thus lag behind. You shouldn't suspend/save the state of Whonix-Gateway. Rather power the Gateway off, if you no longer need it. [4] You can suspend/save the state of Whonix-Workstation, but then the clock will lag behind. To fix it run inside Whonix-Workstation Start Menu -> Applications -> System -> Whonix Timesync.

The host system clock synchronization mechanism still uses unauthenticated NTP from a single source. This is not optimal, but there is no real solution to this problem. [5] The ISP and/or the time server could either non-intentionally or intentionally (as an attack) introduce a clock skew or the host clock could simply malfunction.

If the host clock is too much off, more than one hour in past or more than 3 hour in future, Tor can't connect to the Tor network. [6] The easiest fix in this situation is to manually fix the clock on the host, to power off Whonix-Gateway and to power on Whonix-Gateway again.

Another side effect of the host clock being too much off is, that downloading operating system updates on the host and cryptographic verification, such as verifying SSL certificates on the host browser may no longer be possible, until you manually fix the clock.

Before you think, your ISP is tampering with NTP, ensure first, that not simply the host clock is defect due to an empty battery.

If you should really ever catch your ISP tampering with NTP, you should probably disable it and manually update the host clock out of band, i.e. using a watch or atomic clock. In case it isn't a large scale attack, but a targeted attack, you most likely have already bigger problems to worry about than NTP. (See Warning page chapter Confirmation attacks.)

You have also another option. You could disable NTP on your host and always manually adjust the clock out of band, i.e. using a watch or atomic clock. This might make your clearnet traffic more fingerprintable [7], since it introduces a device issuing clearnet traffic (at least operating system updates, I hope), but not using NTP. I don't know how many people deactivated/broken/uninstalled/never installed NTP. Neither I know, how many people are using alternative time synchronization methods such as authenticated NTP, tails_htp, tlsdate or similar. Search engine research however suggests, that very few people care and do so.

Resumen:

Needs to be done only after importing the Virtual Machine: Modify --biossystemtimeoffset for all Virtual Machines.

Run Secure Network Time Synchronization after suspend/save/resume or do not use suspend/save/resume at all.

Tor can't connect if the host clock is too much off. In this case manually fix the host clock, power off Whonix-Gateway and power on Whonix-Gateway again.

Keep an eye on the host clock, ensure that it's always somewhat accurate.

Even though it's a difficult topic, you are advised to read Technical Design chapter Dev/TimeSync.

↑Otherwise Tor can get confused if time is more than 1 hour in past or more than 3 hour in future and will only reconnect to the Tor network, if clock is manually fixed or powered off and powered on again.

Host Security

Recommendation to use Whonix with Physical Isolation

Whonix using Physical Isolation, setup using two different computers AND virtualization. This is the most secure Tor configuration to date. Unfortunately, it is difficult to setup. See Isolation| Physical Isolation.

These are only pointers for you to search the web about these topics and these are probably beyond the scope of this guide.

One VM

One VM is deprecated. It was tested and developed for 0.1.3. The concept worked. It's deprecated now, because it has no maintainer.

Alternatively, you could also use one VM instead of two, where Tor runs on the host. It has some security and other kinds of advantages/disadvantages listed in the article. See OneVM.

Separate user account for VirtualBox

Security-wise it makes sense to create a separate user account just for using VirtualBox, which is not in the admin/sudo group.

DMZ

If you are using a shared network, as in a cable modem/router or ADSL/router setup, that is shared with others, you should consider configuring a DMZ for your Whonix-Gateway.

This DMZ would restrict the Whonix-Gateway from accessing and from being accessible by other nodes on the network, eg printers, phones, computers, laptops, even if root access was somehow achieved on it.

Should an incursion occur, it would prevent the adversary from exploring other systems and possibly compromising them. It won't however do anything to protect your anonymity, because they could just ping some remote server and discover your real IP address. Or should other systems be compromised, it would be more difficult to compromise Whonix-Gateway.

Host Firewall

Computer Security Education

Port Scan

Using a port scanner service on the internet to test your local LAN's router/firewall is a good idea, if you are careful to find a legitimate one instead of somebody who only wants to sell you something and will give you false positives deceptively. That's good, but even better is to run a port scan application from an external IP to scan your own IP. Either remote login (ssh) on some external machine of your own or proxy through an external IP to scan your own IP. The details on how to do so are outside the scope of this document.

However, if you are not using a stand-alone machine, but are on a LAN with other PCs, it is important to keep in mind that these testing services or your own port scan application from an external IP, actually only scan the local LAN's router/firewall, but these tests do not test your actual host's PC, which, if badly configured, could be susceptible to attacks from other machines within the LAN, behind the router. A false sense of security could be the result.

For example if you share your LAN with flatmates, who are not so sophisticated in computer security, you should regard their machines as possible malicious (may be conquered by a botnet already). Therefore you can not trust the output of a port scan application running on their machine. If you have no spare machine of your own, you could eventually boot their computer from a Live CD, which includes a port scan application, to scan your machine. The details on how to do so are outside the scope of this document.

NAT Router

Being behind an ordinary NAT router may be another tiny extra layer of security.

Conexión dedicada

If possible, not sharing the network (LAN, Wi-Fi, hotspot) with other possibly compromised machines is safer.

Filtering Ports

Introduction

From time to time someone asks, which ports incoming/outgoing Whonix-Gateway requires. The answer is.

Outgoing

Filtering outgoing ports is difficult, since Tor entry guards (or bridges) listen on a variety of different ports. Limiting ports Tor uses for outgoing traffic is possible, although recommended against, since it reduces anonymity (fewer entry guards (or bridges) are available to you). If you want to do so anyway...

Hardware Security

It's recommended to use "clean" computers made of parts manufactured by reputable companies and to pay in cash so as to not have hardware IDs leak your identity.

Whonix doesn't do anything against hardware backdoors.

Ataques físicos

Introducción

Physical attacks require an adversary to be physically preset, i.e. to be able to touch your computer.

Full Disk Encryption

Note that as said on the warning page, Whonix is not designed as an amnesic operating system.

To protect against theft or robbery, power off your machine at times when this is more likely to happen (traveling) and use FDE (Full Disk Encryption) on the host. When using FDE on the host, you shouldn't keep any unencrypted files on that same physical media. It is advisable to move the /boot partition to separate USB media and install Grub, the bootloader, to it. See Pwning Past Whole Disk Encryption.

Also note, during creation of Whonix, a swap partition gets created and added to /etc/fstab.

Side channel attacks

Needless to say, that also FDE does not protect against these threats.

Screen lock

Always lock the screen of the host (or better shut down) if you leave the system unattended.

Contraseña de BIOS

Can't hurt to have BIOS password for BIOS setup and boot. After you are done installing, allow only booting from HDD.

Cold Boot Attacks

Due to how modern computing works, basically everything that you have done during a session is stored in the RAM. If an attacker has physical access to your computer when you are running Whonix, it may enable her to recover everything that have been achieved during the session - even if you are using Full Disk Encryptoion. From typed texts to saved files, including passwords and encryption keys. The more recent the activity, the more likely it is that it is still in the RAM.

Furthermore, it has been shown that the data present in the RAM might be recoverable for seconds or even minutes after the computer is powered off using a cold boot attack.

In both cases the RAM contents can be analyzed in a computer forensics laboratory which might turn into a major disaster depending on what they find.

As far as the authors know, cold boot attacks are not standard procedure within law enforcements and similar organizations anywhere in the world yet, but it might still be good to be prepared and stay on the safe side.

Wipe RAM on shutdown (e.g. using a kexec script) - or do not leave the computer unattended immediately after shutdown. Unfortunately there is not yet an upstream script, to implement wiping the RAM on shutdown. We can not provide a solution for this attack, this is solved nowhere but partially in Tails and Liberte Linux (not checked), waiting for upstream solution, see Dev#Wipe RAM panic script. It's up to you to implement a panic button which will wipe the RAM, please Contribute. The least you can do is Vote at upstream for the feature.

Hypothetical... So, what should you do when you hear an attacker knocking at your door? You could just press the hypothetical panic button on the host. It would start to wipe the contents of the RAM by filling it out with random junk, thus erasing everything that was stored there before, including the encryption key of the encrypted storage devices you might use and the traces of your session. Then you would wait, possibly trying to buy valuable time by barricading your door.

Evil Maid Attack

Problematic Interfaces

Some interfaces such as ExpressCard, PCMCIA, FireWire or Thunderbolt may depending on the host operating system settings allow an attacker with physical access to read the RAM. You are advised to securely configure those interfaces, to disable them or to remove them.

Operating System

About Debian

Debian Announcements

Since Whonix is based on Debian, it takes advantages of the all of the work done by the Debian security team. As quoted from (http://security.debian.org/):

Debian takes security very seriously. We handle all security problems brought to our
attention and ensure that they are corrected within a reasonable timeframe. Many
advisories are coordinated with other free software vendors and are published the same
day a vulnerability is made public and we also have a Security Audit team that reviews
the archive looking for new or unfixed security bugs.
Experience has shown that "security through obscurity" does not work. Public disclosure
allows for more rapid and better solutions to security problems. In that vein, this
page addresses Debian's status with respect to various known security holes, which
could potentially affect Debian.

Consider also subscribing to the Debian security announcement mailing list.

Harden Debian

Most hardening steps can not be easily added by default to Whonix. Mostly the user has to understand them and to be aware of them, require knowledge and effort, otherwise one thing or another will break. This is still under investigation and open for suggestions. Having a secure operating system will always be an important topic.

In conclusion, the main repository gets most attention and security updates. It would make sense to tweak /etc/apt/sources.list and to only use software from the main repository and to only install security fixes, no other updates.

Whonix currently doesn't do that by default and it's an open question for research if that really improves security.

About grsecurity

Linux kernel is not a secure OS, Linus himself made it pretty clear that he doesn't think highly of the "security community"[1]. His threat model and a Tor User threat model don't have much in common. Good that Linux is open source and if we disagree with a policy or politics we can just patch or fork it... Grsecurity/PaX is the most comprehensive kernel patch providing much needed security hardening both for the kernel itself and for making userland protections more effective.

Sadly Debian does not ship a grsecurity kernel. [2] That means either a packager/maintainer of Whonix needs to compile them EVERY TIME there is a security update to the kernel (which is pretty frequently) or the Whonix users themselves need to compile and update their kernels. This is undesirable because kernel compilation is not set and forget, you need a bit of knowledge, it takes a while, especially in a resource restricted VM and you need to keep updated about new releases via mailing lists or similar because your software updater doesn't automatically handle custom kernels (even emerge in hardened gentoo doesn't). All this would most likely only result in users running old, outdated kernel versions.

Furthermore, for Whonix-Gateway and the Identity/Location TCB grsecurity only addresses a subset of security risks: It can mitigate some kernel vulnerabilities (and we only really care about the networking stack which is pretty secure judging from its track record). Maybesome (memory corruption) vulnerabilities in apt-get and Tor that aren't already mitigated by the existing userland hardening done by Ubuntu. It can't protect against backdoors or security issues related to design, policy or yet unknown classes of exploits. We feel that these relatively small advantages outweigh the issues introduced by using a custom compiled kernel. We hope a binary distro will step forward and start using grsecurity. In that case we'll most likely switch Whonix-Gateway to that distro as soon as possible.

For Whonix-Workstation the benefits are even more doubtful. To be effective grsecurity needs to lock down some functions that are needed by Xorg, JIT compilers... but we need those to be working. To solve this we'd have to write a restrictive RBAC policy which is far from trivial. We think accepting that Whonix-Workstation will be exploitable and acting accordingly (using snapshots and rolling back to clean state) is the right approach for a desktop system.

If you disagree with this assessment or have any suggestions how to improve the current situation please let us know.

Vulnerabilities at Install Time

Introduction

VM images that are built with frozen sources rather than current sources (including Whonix)

is that latest stable releases sometimes contain vulnerable, remotely exploitable applications that are very likely to be used over untrusted networks[1] that are in a position to run man-in-the-middle attacks. One example of this is [CVE-2014-6273] in apt-get.

Please help research and document sane and effective solutions. Forum discussion.

Possible Solutions

apt-cache

Whonix-Gateway (when using virtual machines) could be configured to use the host apt-cache. Physically isolated Whonix-Gateways could use an apt-cache running on a separate machine. apt-cacher-ng is an example implementation of such an apt-cache.

Operating system updates would not be anonymized by default, which would be a big disadvantage[2]. One would have to figure out how to configure apt-cacher-ng on the host to download through Tor.

Eventually Whonix-Workstation could use an apt-cache that is running on Whonix-Gateway. This would increase Whonix-Gateways's attack surface once Whonix-Workstation is compromised while decreasing Whonix-Workstation's attack surface when using a vulnerable apt-get to download through untrusted Tor exit relays.

apt-offline

Somehow using apt-offline to do the initial updates of Whonix-Gateway and Whonix-Workstation.

Building from Source Code using Current Sources

Self-created builds from source code using current sources would solve this. However, frozen sources have been implemented for reasons explained in the "Current Sources" chapter. Using Current Sources comes with its own issues.

Always Up to Date Builds

A good solution for end users; however, the maintenance effort (building, testing, uploading) is beyond our current ability. We need help with testing and with an automated test suite for Whonix.

Virtualization Platform

About VirtualBox

VirtualBox is developed by Oracle, a company which is known for not being very "open". That includes how they announce security issues in their products as well as how they are perceived by the security community and how they will communicate with each other.

VirtualBox is primarily a simple, "user friendly", desktop solution and most certainly not designed with our threat model in mind. I haven't heard of anyone seriously auditing the code and I'd like to recommend a different VM solution at least as an alternative. There's KVM and Xen, open source but not cross-platform. It seems they are still lacking in terms of a reliable "internal networking" feature which Whonix heavily depends on. (If you know more, please edit this paragraph).

Anyone looking into Whonix solely because of security should really consider using Whonix with Physical Isolation.

Whonix-Workstation Security

Hardening

Introduction

Whonix isn't a perfectly hardened system. Additional hardening would be very welcome. At the same time, hardening by default is very difficult. That's why this is outside the scope of the Whonix Anonymous Operating System project, unless the project gets serious amounts of help with it. Hardening is left to the upstream operating system. See Operating System for details.

AppArmor

SELinux

SELinux is more robust than Apparmor because its label based vs file-path based. But his comes at the expense of being difficult to write policies. The good news is if you are a KVM user and want to harden your GNU/Linux host, its as simple as enabling SELinux and libvirt will automatically take advantage of it without any further effort needed on your part.

These instructions apply to Whonix and could be easily replicated for your Debian host.
First disable Apparmor if you are using it. Both MAC systems cannot be run simultaneously run. This is not supported by LSM and may also be a source of conflicts.

AppArmor is disabled, and the kernel module unloaded by entering the following[3]:

sudo /etc/init.d/apparmor stop
sudo update-rc.d -f apparmor remove

To enable SELinux follow these steps.[4] The cited guide also includes steps for writing custom policy for hardening.

# aptitude install selinux-basics selinux-policy-default
# selinux-activate
# reboot
# sudo nano /etc/default/grub
Replace all mention of apparmor in settings for GRUB_CMDLINE_LINUX with selinux=1 and the enforcing=1 parameter to the Linux kernel. The audit=1 parameter enables SELinux logging which records all the denied operations.
Remove the line under it that starts with: GRUB_CMDLINE_LINUX_DEFAULT
# update-grub

Alternatively, less secure than Multiple Whonix-Workstations, you could start multiple instances of Tor Browser and run them through different SocksPorts. The instructions in the Manually Downloading Tor Browser article need minimal changes.

Using multiple Whonix-Workstations

Second, Optional, Extra Firewall

There is a Second, Optional, Extra Firewall for Whonix-Workstation, which is disabled by default. You find it inside Whonix-Workstation in /usr/bin/whonix_firewall.

Read the script comments and decide if you want to use it.

Whonix-Gateway Security

Static VirtualBox IP

Instead of using DHCP to obtain the internal IP for Whonix-Workstation eth0 NAT adapter, you could also use a static IP instead. Perhaps this could (minimally?) improve security, since you can remove one more package: the DHCP package.

Open /etc/network/interfaceson github, read the comments, comment out DHCP and comment in Static VirtualBox IP.

Disable Control Port Filter Proxy

Introduction

Disabling Control Port Filter Proxy (CPFP) can improve security while sacrificing usability. You will receive helpful notifications when Tor is not fully bootstrapped anymore by multiple tools that come with Whonix.

Tor Browser Updater

If you want to update Tor Browser using Tor Browser Updater by Whonix developers... There is a bad and a good news. Bad news first. Unfortunately, there is not yet an option to skip function tb_connectivity_checks_tor, that relies on CPFP. (That function has been added in a to be released version. [6]) However, the good news is, you can use update-torbrowser in non-interactive mode using the --devbuildpassthrough switch. Note,

that it will kill any eventually running instances of Tor Browser / firefox without asking, so close your browser sessions before attempting to update.

it will by default not use Stream Isolation (proxy settings), but by using its CURL_PROXY variable [7] as described below, you can configure stream isolation.

works only if folder /home/user/tor-browser_en-US does not exist.

it wouldn't stop if the download server were to run an endless data attack [8][9] However, it can be compensated by either manually terminating update-torbrowser or by using the timeout utility as in the example below.

If you think about it, it becomes clear why the connection happens in reverse order. Whonix-Workstation has no way but to go through the Proxy-Gateway. The Proxy-Gateway has no way but to go through Whonix-Gateway. The last one in the chain, in this case, the VPN-Gateway, must obviously connect through clearnet. Thus, the VPN-Gateway uses clearnet, the Whonix-Gateway uses the VPN-Gateway to connect, the Proxy-Gateway uses Whonix-Gateway to connect and Whonix-Workstation uses the Proxy-Gateway to connect. Since the Proxy-Gateway has no way but to go through Whonix-Gateway followed by VPN-Gateway, it's clear why it will be the last hop in front of the destination server.

Whether such combinations make sense or not is controversially discussed and depends on your personal threat model, see Tor plus VPN or Proxy.

You must know, understand and edit /etc/network/interfaces on Whonix-Gateway and/or on Whonix-Workstation (and if not using physical isolation, the virtual internal network name in VirtualBox settings).

It will be difficult, because there are no other Anonymizing Gateways (VPN/JonDo/I2P/Proxy/SSH/VPN) available for download besides Whonix-Gateway which uses Tor to anonymize traffic, which you already know about. You have to look for instructions (there are some for a pfSense based VPN-Gateway you can find using a search engine, but untested for leaks, which does not imply, that there are leaks) and/or build such a Anonymizing-Gateway yourself.

MAC Address: If you are interested in the discussion about anonymizing MAC addresses, you could read the development discussion and draw conclusions from it, see Computer Security Education MAC Address].

Of course you should read all Documenation pages. (Although some stuff will not be of concern for you. For example, if you are not interested in TorChat, Remailers or Mixmaster, you obviously don't have to thoroughly study these pages.

Design: Still reading? Great! Please check the Technical Design, it contains further recommendations on what is less than ideal and how it could possibly be improved.

Notas

↑Leaks list of installed packages to ISP level adversaries and update servers. You usually don't want them to know that you installed a webserver and therefore likely host a hidden web service and so forth.

This is a wiki. Want to improve this page? Help welcome, volunteer contributions are happily considered! See Conditions for Contributions to Whonix, then Edit! IP addresses are scrubbed, but editing over Tor is recommended. Edits are held for moderation.Whonix (g+) is a licensee of the Open Invention Network. Unless otherwise noted above, content of this page is copyrighted and licensed under the same Free (as in speech) license as Whonix itself.